1. Field of the Invention
The present invention relates to a ferrule holder assembly for an apparatus for grinding end faces of a plurality of ferrules with optical fibers simultaneously.
2. Description of the Related Art
It is well known by those skilled in the art that in order to connect optical fibers together while reducing connection loss and reflected returned light, tips of ferrules are ground by perpendicular or inclined spherical grinding to connect the optical fibers together. The shape of the convex spherical surface in this case is standardized by the international standard (IEC: International Electrotechnical Commission No. 60874-14-6) or the like. U.S. Pat. No. 5,351,445 discloses a technique of apparatus for grinding end faces of a plurality of optical fibers simultaneously. A ferrule holder of this grinding apparatus projects tips of ferrules from a plurality of insertion holes (sleeves) thereof to a grinding board by a specified amount and supports the ferrules. Grinding is performed by revolving a grinding film put on an elastic plate of the grinding board by an autorotational and orbital motion mechanism of the grinding apparatus and applying a specified amount of pressure to a grinding jig on which a plurality of ferrules with the optical fibers are mounted. Thus, the shape of the tips of the ferrules of the optical fibers can be made convex spherical surface that satisfies the standard.
Even if a similar type of ferrule or connector is used, however, variation in length exists within a dimensional tolerance and the size differs depending on the manufacturer. Therefore, when a plurality of ferrules or connectors are mounted on the ferrule holder, it is difficult that all the tips of the ferrules are projected by a specified amount and supported.
Although a reference plane of the ferrule holder for mounting the ferrule for grinding is processed to have a specified height with a strict tolerance, since the reference plane for mounting the plurality of ferrules is fixed, the heights of the tips of the ferrules from the insertion holes vary by an amount of variation in length of ferrules or housings of the ferrules.
When the plurality of end surfaces of the optical fiber connectors of a lot in which the lengths of ferrules vary are simultaneously ground, since the grinding holder is directly weighted in the conventional grinding apparatus, problems occur in that the holder is tilted due to the variation in projection amount therefrom to generate a deviation from the shaft axis, or the ferrules having a small projection amount are insufficiently ground. Therefore, in the method of the conventional grinding apparatus, it is necessary to perform preliminary grinding up to a shortest ferrule and then to perform grinding again from a state in which the ferrules have the same height.
Accordingly, it is an object of the present invention to provide a ferrule holder assembly for an optical-fiber-end-face grinding apparatus in which the aforesaid problems of the variation in length of the housings of the ferrules can be solved.
In order to achieve the above objects, a ferrule holder assembly for an optical-fiber-end-face grinding apparatus according to the present invention includes a ferrule holder board provided to be moved upward and downward in parallel with a grinding board of the optical-fiber-end-face grinding apparatus, a ferrule sleeve provided at the ferrule holder board for receiving and supporting an optical fiber ferrule while putting the tip thereof at the grinding board, an adapter for retaining the optical fiber ferrule or a connector for supporting the optical fiber ferrule in a state in which the optical fiber ferrule is inserted into the ferrule sleeve and urging means for urging the adapter in a direction to the grinding board from the ferrule holder board.
The adapter retains and supports the optical fiber ferrule or the connector for supporting the optical fiber ferrule at the ferrule holder board in such a manner that the ferrule can be slid to the ferrule sleeve in the axial direction thereof, its revolution is restricted, and the downward movement limit is specified relative to said ferrule holder board.
A retaining part of the adapter has a hook structure corresponding to a retaining member of a plug-type optical fiber connector housing.
A retaining part of the adapter has a screw structure corresponding to a retaining member of a plug-type optical-fiber connector housing.
The ferrule holder assembly for the optical-fiber-end face grinding apparatus is a ferrule holder assembly for an optical-fiber-end face grinding apparatus for inclined grinding, the attaching angle of said adapter is the same as that of the ferrule sleeve, and a guide key groove of the adapter is formed only at one side.
The urging means is a coil spring and the force of the spring is smaller than the urging force of springs assembled to the connector plug itself.
The means for urging the adapter to the holder is a coil spring and the weight is 550 gf or less appropriate for spherical grinding. The ferrule holder assembly for the optical-fiber-end-face grinding apparatus according to the present invention includes adapters in each of which the ferrule or the housing is fixed to a grinding-jig-plate main body thereof having a plurality of insertion holes penetrated for receiving the outside diameter of the tip of the ferrule. By pressing the adapter with a spring pressure, the ferrule with the optical fiber can apply a specified pressure toward a grinding board.
In this case as well, although the heights of the tips of the ferrules from the plurality of insertion holes vary, the pressure of the tips of the ferrules to the grinding board can be almost the same by setting a spring constant of a spring that presses the adapter small in spite of the variation in the ferrules and the housing, and thereby the variation can be absorbed. Thus, the variation in the shape of the tips of the plurality of ferrules after grinding can be reduced.
In addition, even in the inclined spherical grinding, the variation can be reduced by providing the insertion hole of the grinding-jig-plate main body in a manner so as to be inclined relative to the grinding surface, and also by inclining the adapter having a mechanism to be pressed by the spring pressure.
The object to be ground is not limited to the ferrule, but various kinds of connectors can be applied depending on the design of the adapter.